Insulating product and its manufacture



3,042,573 Patented July 3, 1962 i 3.042578' IFFL'LA'HNC PRODUCT AND [T5.l \XL'FACTL'RE Paul S. Denning, Risdr-uuec, l-l:t.. zs'iznor to Johns-)l'nmillc lerlitc Corporation. a corporation of Illinois. No Drzmlrtg.rim: Sept. 1?, X955, Scr. No. 535.305 25 Claims. ((1.162-171) Thisinventionrelatcs to thermal and acoustical insulatin; mnterinls andtheir manufacture 'l'hc product is csvcntinlly cxpnr-Jcd p:rli=e. hcldtogcthtr by a netuork o! fibcr prcfrably treltcd .lb a tack increasingsubstance to increase tlt. ctlcctiv: length of the fiber by inncnsingthe mutual friction or uck'of the prod-acts and their n-:thods ofmanufacture lrcrcinaltcr described.

This application i' a continuation in part my copcnding applications:r..tl No. 4l,533. filcd July 30, l948; Serial No. 370,415 a: ll SerialNo. 422.096. nc'w all abandoncd. The said ro-ponding applications mainlyclaim "various features of the product and methods of manufatturc.

l have dis-covered tnnt expanded pcrlite even hen as finc as that usedin the illu trative products of this and the-above parent applicationsis very t'rrc filtering, that is, it tle-waters quickly. This isintrortnnt in the illustrative method of making the product wherein thesolids are dispcrscd in an aqueous slurry of pcurable ccusistcncy(though of vastly greater concentration than conventional fiber siurricsused in the manufacture of fiber board and 1h:- likc) and then formedand tic-Watered. Suzh a slurry may b: very rapidly de-zvatercd ascompared with the time required to dc-watcr the fiber slurr (with orwithout other aggregates or fillers) heretoftrc used for the forming offiber board. This is a proprrty peculiar to pcr'zitc as compared withother insulating aggregates such, for example as exfoliated vermiculitewhim is very slow filtcring (regardless cf particle sizt) due to themultitude of contacting fiat faces and lamina characteristic ofcarfoli'ltcd vermiculite. As stnlcd above, the product is essenticlly amass of expand-d pcrlitc particlcs contacting each other only in limitedareas sulficent to prove shrinkage yet leaving the mass "open" toreceive the fibe network or skeleton without impairing rapid dc-wvhrin".The amount of fiber used is generally small compared to tho large volumeof pcrlite (one illustrative volumetric rat o being about 5 or 7 ofpcrlilc to l of fiber).

Preferably, the proportion of fiber is limited to what is cccssary togive adcouatc strength to the product, because additional fiber wouldunnecessarily reduce the deateriug or filtering rate. Since the fibcrslie mainly in the interstices between the granules of :mrI-ite, thefiber docs not substantially increase the volum; o the product over whatit would be with no fiber added. ln on: type of expanded pcrliicgranules of which abott 70% are minus 16 and plus 50 mesh. about 48% oft: .otal volume comprises voids between the granules. This means thatfiber equitalent to about 48% of thc tota voume of the pcrlite might beadded without increasing the volume of the final product over thatdetermined by the pcrlitc alone. Actually, of course such a high amountof fiber is not only unnecessary but actually obiectional.

The significance of avoiding increase in volume over that determined bythe pcrlite alone is this: If so much .tli': fibers may lie withoutincre fibcr were added as to caus: inzrcsse in volume over that of the'perlite \sithost fiber, tlur: would be substantial shrinkage of theproduct cn drying. Shrinkage is c aiously objectionable; A mass ofpxlit: alone does not substantially shrink on drying because thcgranule-s of palilc are in substantial contact vsith 2:,- surrcundinggranules and since they act as though they crc gccerzliy spherical incharactcr, they protiie intersticcs in with g the volume of the massover that of thc pcrlitc alcnc. and drying out of the water held by thofibers does not, tbcrcforc. result izi shrinkage of th: 'trctluct. .111:mm generally spheri is employed to describe the nature of the contactsbetween granules rather .lnn their literal shape. L11: sphcrcs. theycontact in points rathcr than in surfaces v.hcrein capillarity wouldoperate to hold water and thereby resist dc-wntcring; and like spheresthey prosi c spaces where fibers may lie without increasing the volrzs:of the mass of granules alone. Axually, the grass. may have (but notalways numrvus points proiec'ing from them (cal ed rabbit vars" in thetrade) uhich have the same effect as spherical aortas-5,05 limitingcourses to points rather than surfaces. v

The fibers. on the other hand, zr mainuined by 73;: pcrlitc particles inthe form. of an opcr: net work and held against segregation which wouldretard d-wston'zg. The pcrlite particles provide such a fine grainedteams: as to leave no large voids where a substantial large urnher offibers may collect 811i b!oclc the void: and interfere with rapidtie-watering. The open tex ure of the 55::- nct work maintained by theperlitc and substantial absccca of bunching or segregation of thefibers, is further r:- veriled by inability of the livers to retain orhold a. substantial amount of water during the (lo-watering prccsszs, ascompared with products in which a substantial number of fibers are closetogether. The product may, therefore, be tie-watered to what is termsd adry condition, lea'dcg much less water to be remo ed by drying vn'thheat.

Except for the foregoing considerations and those out enumerated, thefiber may be varied from the above H trated ratios. if increased, itprovides some increase in strength but with sacrifice -f izsulatingefficiency. nonoombustibility and rapid d-a-watcring properties andincrease in cost. For example, if the product has as high as 30% byweight of vegetable fiber (such as newsprint) it begins to lose some ofits rapid tie-watering specd. With 20% by weight of newsprint. Lbsproduct has ade quate strength, i.e., a modulus of rupture of 45 poundsper square inch.

Ratios by weight between the fiber and perlite vary with the nature anddensity of the fiber. The contro ling relationship is actually the ratiobetween numbers of individual fibers and the numbers of particles offine perlite, but there is no practical way of counting either numbersof fibsr or pcrlite par icles. Hence, in doscribing the invention theratio can be has: expressed either by volume, or preferably by weightfor each specific fiber or other variable constituents. The preferredratio (fiber to perlitc) by weight of newsprint and similar wood orvegetable fiber is about 20-30 parts by weight of fiber to 70-80 partsby weight of pcrlitc, but for the same number of commercial asbestosfibers (for exam plc) as paper fiber, the weight of the asbestos fiberwould be'much greater because asbestos has a high specific gra'ri ty andit is not practically possible to sub-divide asbcstos into itsultirF-ate fibers, a fiber actually comprising a bundle of fibers.Commercial asbestos fiber has a specific gravity of about 2.5 whereaspaper or wood.

fiber has a specific gravity of .6 to .7. Therefore a given number (orvolume) of absestos fibers is very substantially heavier (about 4 times)than the same number Percent Perlite 60 Asbestos fiber 30 Kraft fiber 10the ratio of the several constituents by volume is approximately PercentPerlite 93.33 Asbestos fiber 5.34 Kraft fiber 3.23

if the total volume of the product (including the voids between theperlite granules, about 48%) were considered, the volumetric ratio offiber to pcrlite would be still lower.

The above volumetric relationships demonstrate that the product isessentially perlite and not fiber adulterated with perite. Further, thecircumstance that the product will not support corhbustiorl (even thoughall the fiber be vegetable) demonstrates how well the fibers areseparated or isolated from each other, and how small the proportion offiber actually is.

The illustrative product may be made from perlite ore which ispreferably too fine for use for plaster and concrete aggregates. Suchore is generally from minus 50 to plus 100 mesh, which results in a highpercentage of expanded perlite which should preferably not be used inplaster or concrete aggregates. However, the product is not limited toparticular ore sizes or to a specific range of sizes of the expandedpcrlite granules, except preferably not more than 2 to 5 percent shouldbe finer than 325 mesh (ie. 44 microns) and preferably not more than 20%should be larger than 8 mesh. However, large granule sizes, assumingthat there be an adequate range of smal!cr sizes, are objectionable onlyto the extent that they may tend to fioat to the top in an aqueousslurry and thereby segregate. The present process, hereir fterdcscribcd, is adaptable for use with crude perli cs, but in expandedform in a. wide variety of classifications or grade: of crudes. Theparticular grade of crude perlite ore, as mined, often determines theparticular grade of exparded pcrlite available for the manufacture ofthe instant board. The following grades of pcrlitic ore and expandedperlitc are adaptable, for example, for use in the manufacture ofinsulating products according to the present process:

(1) Crude ore which has an approximate screen analysis of plus 100 meshand 80% minus 100 mesh which produces an expanded perlite having anapproximate screen analysis of 70% minus 16 mesh plus mesh (weighingapproximately 2 /1 to 3% pounds per cubic foot),

(2) Crude ore having an approximate screen analysis of 92% plus 40 meshand 8% minus 40 mesh, which produces an evpanded perlitc having anapproximate screen analysis of 93% plus 100 mesh and 7% minus 100 meshweighing approximately 3 pounds per cubic foot),

(3) Crude ore having an approximate screen analysis of 75-80% plus 100mesh and 20-25% minus 103 mesh, which produces an expanded pcrlitehaving an approximate screen analysis of 91% plus 100 mesh and 9% minus100 mesh (weighing approximately 3 pounds per cubic foot),

(4) Expanded perlite, the major portion of which passes a 20 mesh screenand finer with a substantial portion 100 mesh, and

(5) Expanded perlite, the major portion mesh and finer with asubstantial portion 100 mesh.

It is possible to effect a m'utture or selection of various grades,utilizing particularly those rades not suitable glass, as'c for thecnzzufacture of other tTQdUCiS, iQ tL{If-Pl, aster concrete a crecategt.The following ear andcd 5' gs are'a.so sortable for use in the instantanufactuting the board of this invention:

(l) Expanded pcrlite, substantially 100% passing through 30 mesh andpreferably '1- passing through 50 mesh. Preferably, substantiflly noneof it should be coarser than 20 mesh.

(2) Erpzccicd perlite of which the particles are 65 mesh and finer.

(3) E and 4!.2 minus 65 mesh, with substantially none coarser than 20mesh.

Generally speaking. the expanded pcrlite used for the manufacture of theinsu.aling board of this invention should be of a. grade such that amajor portion, or at least a substantial portion be capable of passingthrough a 20 me h screen and a substantial portion be of approximatelymesh grade or finer.

The term pcxiite is used herein in a generic sense to include pcriiteand perlitic vesiculating materials generally.

To distribute the relatively small amount of fiber uniformly tlt' "boutthe large bulk of expanded pcrlite particles, :t fiber such as newsprintor other relatively short veg le or mineral fiber (cg. glass wool, fibercs) is preferably used. Newsprint fiber (which F E: advantage ofrelatively low cost) has an average of about with a maximum length ofA", \vhcrc lLraft fiber (which may also be used, though it is moreexpensive) has an average fiber length of about I /4 to 5's" Asbestosfiber of jD Canadian grading is short enoue': so that about 'd'ifill p55 tbm lgh,.a.c4.,xnesh screen and :1. c retained oh a ntcshscrcen. Whie M sMwWw =21: of long hoer (vegetable or mineral) can a sma araalso bed5 atcd throughout the perlite, it is dimcult to substitute fiber(despite the advantage of its greater strength) e 'cly for the shortfiber. Long fiber bunches if it be p in any substantial amount, andthereby takes di. uniform distribution of it throughout the slurry.

To obtain strengths comparable to what would be obtained if long fibercould be used substantially exclusively, the short fiber is preferablytrreatcd to increase its mutual friction or tack by applying thereto arelatively mall amount of a non-migrating friction increasing substancedisp ible in water. In the illustrative method such substance ispreferably added to the aqueous slurry containing the fiber in the formof an emulsion or dispersion to permit distribution of the relativelysmall amount over the relatively large surface of the fiber. It tends tocoilect on the fibers rather than on the perlite particles. Forconvenience such substances will be referred to herein as a tackmaterial or substance adhesive, or bi-.;er. It should preferably benon-migrating so that it will remain on the fibers and not travel to thesurface with the water as it is removed from the product or concentratein the surface of the product on drying. This excludes most truesolution even though they have tacky characteristics. For most productsmigration of the tack substance to and concentration in the surfacelayer of the product, is not desired, though where a very strong andtough surface layer is desired, some migration may be perrritted. Inmost such cases, the interior of the product would be correspondinglyweaker.

It is believed that the adhesive in crcases the friction bewfibcrs anance to being pulled nded perlite, 59% of which is plus 65 mesh asfillers. While it is believed that the adhesive sabstance board also hasthe appearance of a board coczairiag fiher and perlite held together bya binder. As a result. while it is believed that a tacking actionbetween the fibers and the adhesive occurs and very little tacking takesplace between the perlite and adhesive, for the pur -axes of thisinvention the adhesive may also be considered as a binder.

In general and independently of the specific fiber and taclt substanceused, the ingredients of which 1!..- board is comprised should bepresent in amountwt in accordance with the following approximatepercentage ranges: eztpanded p-r 22-10% and a MMM' 3 for mostcommercially attractive products not more than apprcximately and notless Lnan approximately 5'2: for most products best exemplifying theinvention. Preferably. an approximate general formula by dry weight fora finished insulating andacoustical product lite articles 0' fibers,estve or hinder. up to apptcximatly is: Y Percent Perlite 7O Fiber 15-30 Tacit substance l0-25 To avoid too low a strength, the ratio by ifiber to pcrlite should preferably not be subs: ly less than t to 4%. Aratio by weight of fiber to perlite of about 1 to 3 is preferred. Interms of weight of the product made with vegetable fiber, this is aboct2 3% fi her and 60 to perlite, the balance belie tzcl; substance. Forother fibers the weight may vary tly d5? pending on the characteristics,length, weight and strength of the fiber. Insulating board of thischaracter should not weigh substantially more than 8 to 10 pounds percubic 'foot; but if a tougher and stronger board be necessary weightsmay be increased to 15 pounds per co'cf: foot by greater compression ofthe board during manufacture.

The concentration of solids in the slurry used in the illustrativemethod depends somewhat on the rzethod of manufacture. When the productis formed on a cylinder machine or Fourdrinier, the concentration ofsolids may be 3 to 8% to make a product having a dry thckness of atleast one inch. High rather than low conceczation of solids is preferredboth to increase production and to combat any tendency of the largerparticles of expanded pcrlite to rise in the slurry. This contrasts withthe dilute slurries used in the manufacture of conventional fiber boardand paper in which the solids cannot exceed .02 to .5%. When formed in asuction mold the concentration of solids in the slurry may be muchhigher than for a cylinder or Fourdrinier machine. Regardless of themethod of formation, de-watering is very rapid due to the "open" natureof the mass of perlite particles and ab sence of fiber bunching orsegregation.

After and during forming, the board is lighzly compressed to give ituniform thickness and to consolidate it. The-residual moisture(remaining after application of suction and pressing) is preferablydriven out by heat to accelerate drying.

Whether the board is dried in a continuous web or cut in pieces beforedrying, depends on the type of apparatus. Generally it is preferable tocut the web transversely at intervals before entry into the drier. Thedried board is then trimmed to size; and if it be intended for use as anacoustical material, the face'of :..e material may be drilled to provideconventional sound receiving recesses, or a thin layer may be cut fromthe surface if it be desired to increase the porosity of the surface forsound atseew' om- For other uses, surface cutting would be' undeslrzble.

Various binder, tack or friction increasing substances may be used,deprndiag somewhat on the uses and desired propcrties of the product. Inmy said co-pending applications, bituminous :zzulsions, sodium silicate,pitch.

' bentonitc, and various resins and dispersions of starch and cementsare discloses. Light colored tack substances, such as sodium silicate.sczrch and light cofored cements and resinemtsiorts cfszspensions arepreferred for an acoustical or sound inst-.LLi'c-n since they would notbleed through or discolor the :azerial ifpainted. Emulsitied asphalt hasthe advantage of low cost and it gives the product excellent waterrzcerlency, and, surp s ngly, the product will not support. combustion.At very high tem-' another. The same apples to other organic tacksubstances such as starch and resins disclosed in said cope tdingapplications.

The invention is not [Liaiied to the specific taelrsub stancesenumerated, bu considerations ofova-liability,-

cost, etc., practically lir them to tack snbszanzes which are lowin'eost and (s im-n the illustrative method of manufacture is used) arereadily dispcrsible in an aqueous slurry. Other solvehtsec liquid phasesfor the tze-l; substances are costly and :23 be more ditiicult todisperse in water, and they may also involve a fire hazard inmanufacture. Aside from the matter of relatively high cost, syntheticresins cc-i-d be employed. One example is calcium acrylate, a W11.soluble monomer which be comes water insoluble. :1 general, however,water solutions tend to migratetc icsutfaceon dryin and tend,

to concentrate the tack substance in the surface. This is characteristicof mes: soluble tack substances, and it has been regarded as true ofsodium silicate.

W has s e use a ,t.,? "og cmflfs' t't's j'fi' an dhesive has h---tnforcic-cc: limited 0 t oducts in which migration of the so tta concentrationin the surface layer of the product...

has not-been objectionable. For example, sodium silicate uscd tg bondetfi a ted vermiculite in a molded or otherwise form'd' pro cactfbitt ondrying, the water therein or: escaping to "'2 surface carries asubstantial amount of the silicate to the surface where it is left asthe water evaporates. Tia: surf ace layer of such a product is quitestrong and dense cut if it be trimmed off for any reason the remainderof the product, having little silicate to bond it, is very weak- Also,in other products, sodium silicate has been vulnerable to the presenceof moisture and is not regarded as W222. resistant. For these reasons,

although its adhesive pfapertici gtrg gggllg,Otfii4tn silimehas'hgtfgg'f da satisfactory fut products ammonia -tteirtanse sunrise" is astionable or where it may be exposed to moisture.

I have; discovered the; contrary to all $91155}- perience in the use oft e s 'n-n srl ate does not substantially 029215512 y n- 'a'- t the suace in the present ccluct ygich comprises mainly emillgwrlitg I beli eis du'tarasnsrdrme sodium silicate with the perlite itself which is analuminum s licate. My presezs theory is that the reaction between theperlite and ti: sodium silicate increases the viscosity of the latteror-oincrwise changes'its nature so that it migrates less Sodium silicatedoes re aet with glass, Among the evidences tmreaction does take p acebet can the sodium pcrlite and the -.'eg:table fiber silicate andpet-lite, is the circumstance that it pure sodium silicate solution bepassed through a body of expanded periitc, an aluminum silicate is foundin the filtrate. Aluminum silicate is a very refractory bonding agent.Furthermore, increase in the soda to silica mtio (which might occur insuch reac ion) increases the viscosity of the sodium silicate, therebyreducing its tendency to migrate on drying out of the water. Also, thefact thct in some cases perlitc acts as a catalyst may explain theunexpected impairment of its tendency to migrate. Other aggregates donot thus affect sodium silicate. For example, if exfoliated vermiculitebe substituted (in identical volume) for the perlite in the illustrativeproduct, with In) other change, the sodium silicate will migrate sosubstantially that the modulus of rupture of the center 1" core of a 3"thick slab is rcluccd by 40% over the strength of the remaining outer 1"thick pieces of identical dimension. ln :1 similar pcrlite slab, thereis only a sm.-.ll difference in the modulus of rupture between thecenter core of the slab and the remaining pieces, indicating some,though small, migration.

Another indication of a change m the nature of the sodium silicate inassociation with expanded pcrlitc, is the unexpected resistance to disntegration of the illustrative product under prolonged soaking in water.So.;king in watcr'for over a month, while softening the productsomewhat, did not result in disintegration. After drying, the productretained 75% of its original strength. in otherwise identical p oductswherein exfoliated vermiculite rcplcced the expanded pcrliic, completedisintcgration occurred after soaking for 72 hours. As a bending agent,sodium silicate has been notoriously vulnerable to moisture. Itsunexpected resistance thereto in association with A product of thischaracter wiil withstand the severe fire tests specified in FederalSpecifications SSA-l18a, which comprises exposure of a 9 square footarea of the product for 40 minutes to an impinging flame which raisesthe tempczature from room temperature to 1700 degrees F. in 25 minutesand then holds. the temperature between 1700 dc grees F. and 1706degrees F. for the remainder (15 minutcs) of the test withoutsubstantial falling apart of the roduct. The continuous glassreinforcement formed by \the sodium silicate, even though the fibcr becharred,

prevents disintegration of the product under such heat. As stated above,the fiber (if it be vegetable fiber) is too isolated and is present intoo small an amount to assist in propagation of flame or ccmbustionthroughout the product. The very large proportion of periitc acts as abarrier to propagation of combustion aiong the ft'ccrs. The depth ofpcnetr'iion f the charting emperatures above defined, does not exceedabout A inch. Of course, non-combustible fibers such as glass fiber,asbestos etc., may be used, particularly if the product be teaded for ttem eratures which would m lLqg buto erwis c c a -C! *r suc as newsprintor Kraft is preferable from the standpoint of ost and ease ofdistributi'm taroughout the slurry.

The aforesaid tata; su'astances while contribu ing differont incidentalproperties to the proclact, are believed to have the commoncharacteristic of inzreasing the tack or mutual friction between thefibers, increasing their resistance to pulling apart and giving theoduct a strength {equivalent to that theoretically ohtainablcwith longfiber, iii the latter could be uniformlv distributed throughout theproduct, and of etiecting a binding action to coat :inc and 23 formanufacture of a product of this character.

As stated in my co-pcnding application Serial No.' 45.533, dilution withwater beyond what is necessary to :21: g pourable slurry, is prcfcrablyavoided. Even v-EL': such an abnormally high concentration of solidst'c: illustrative products may be readily made to dry thickncsacs of l"and more without difficulty. indeed, the

'ation on thicltncss is not dct:rmincd b the time req d for dcwatcring(because even thicker material may be quickly dcuatcrcd) but by that'licilrtcss which may be 2105! rapidly dried in the drier aftertie-watering, material thicker than 1" requiring more than aproportionally -lo:c;r time to dry. it is preferable, theref re, to ormthe cm: s not substantially thicker than 1" to obtain the most F 'cntdrying and if a thicker board he desired pluof boards mav be cementedtogether to obtain the desired thickness.

Gcncraliy, the board comes from the de-watcring step so dC-WulC-Cd thatit is termed dry" (though it is not .ally dry) and needs little or nopressing before it enthe drier. Gcmrally, a single pair of pressingrolls cs. -Howcvcr,'it should be'ier'ncmbcrcd thatthe suc- 02 used inde-wctcring causes compression of the board to $3.. 2 extent through theaction of atmospheric press'cL-c.

01' course, an even greater concentration of solids may be z'ohncd anddeuvatcrcd in simple suction molds, but

$1.: methods of formation are slow as compared with fermion by acylinder or Fourdrinier machine.

Tani: the low fiber content which characterizes the prznt product.strength varies with the proportion of a- 3: no more fiber is used thanis necessary to hold the per- .n its formed shape. If the fiber c ntentbe increased, tack substance should also proportionately inthe creLaizza ie from the increased proportion of fiber. Within lir ts,depending on the nroPortion, length and strength of the fiber, strengthcan also be increased by increasing thc foot) 7 Fi er (pulpcd newsprint)20 Asphalt (used in the form of an emulsion containing -f=360% asphalt)10 Example No. 2

Percent Expand :d pcrlite 68.2 Nz sprint fiber 9.2.7 Asphalt 9.1

it as #6 I! 51.7 as 45.4 49.3 3". s as. 9 27. 0 2s. 2 as 2.5 2.5 2.51;.0 20.0 25.0 30.0 512 an to 7 5st Where inr'ulating efficiency isparamount, preferd, to obtain the benefit of increase in s rength oaloing; Example N 8 v v V Percent Expanded perlitc c 48 Asbes os fiber 24Kraft fiber 8 Sodium silicate 20 vinyl acetate polymer:

- The sodium silicate employed was 6 to P-. coneentra l tion wl'h a sodato silica ratio of l to 3.36. Although the raft titer chars at thetemperatures to which a board of this character is exposed, it providesa good wet strength during manufac u e. i Other examples are describedin detail in said co-pcnding application Serial No. 41,533.

it the tan color resulting from the us: 02 asphalt as a tack material beobjectionable for any reason, as in an acoustical insulation, lightcolcrcd tack substances such as sodium silicate and those disclosed insaid two-pending application Serial No. 370,415 may be used. Onematerial using starch as a tack substance comprises:

Example N0. 9 Percent by weight 25 Expanded perlite Fiber Cooked starch10 The above product weighs 6% to 7% pounds per cubic foot and has amodulus of rupture of 50 to 60 pounds per square inch. Roughly, theratio 'of starch to fiber is about 0.4 of a poundof's'tarch per pound offiber; while as little as 5% .of cooked starch may be used. bezcerstrengths are obtained with 10%.

Other examples using starch are as foilyas:

The starch gives unexpected water resistance: Prolom edsoaking'of theproduct in water for three weeks resultsin only slightly. softening ofthe metric]. Greater water resistance may be obtained by the addition ofa water repellent material such as a resin emulsion. Additional waterrepellent substance used for an acoustical COltl'd should, of course, belimited to a material which will not obiectionablydiscolor the board.One suitable 50 waterrcpellent substance is an aqueous emulsion of a lnaddition to its advantages in a product subject to high temperaturessodium silicate, because of itsdightcolor may also be advantageouslyused as a tack sub- 55 stance in acoustical installation.

. To insure adequate reaction between the sodium sili- Example No. 14

Percent by weight Expanded pcrlite (weighing 3 to 3% pounds per .cubicfoot) 56.72

Fiber (pulped newsprint) 19.91

Sodium silicate, dry (introduced as a 10 degree B. solution) 23.37

The above product has a modulus of rupture of 106.8 75

cubic foot and is capabiecf ptssing C1: above fire test.

The above strength substantially exceeds What is necessary fortin-acoustical insulation.

Another product employing a lower concentration of sodium silicatecomprises:

Example N0. 15 Percent by weight Expanded perlile (weighing 34% wu'ndsper cubic foot) 59.27 Fiber (pulped newsprint) 20.81 Sodium silicate,dry (introduced as 8 degrees B6.

solution) l9.90

The above product has a modulus of rupture of 79.93

pounds per square inch, weighs 9.11 pounds per cubic foot and will pussthe above fire test.

. A third product employing a sodium silicate solution of minimumconcentration (4 degrees 8:. solution) com- Such a product has a modulusof rupture of 61.11 pounds per square inch, :1 weight of 7.86 pounds per"0 cubic foot but failed, after 18 minutes exposure to the tire test.While the latter strength would be sufficient for rut-acousticalinsulation, if the board were not superficially trimmed, such a lowconcentration of sodium silicate results in some migration to thesurface with the result that if superficially trimmed, to expose themaximum open pores the strength would be less.

Another product embodying asbestos fiber with sodium silicate as a tacksubstance comprises:

Example No. 17 Percent by weight Pe'rlite 48 Asbestos (5D) fiber 24Kraft fiber 8 Sodium silicate .The expression 5D above is a Canadianstandard classification for an appropriate type of commercial asbestoswhich generally identifies the character of fiber by fiber Perlite 4Asbestos fiber Kraft fiber l0 Proportions ofthe several constituents maybe varied considerably in relation to each other, but for productshaving generally the physical properties of those given above, theconstituents should preferably not vary substantially more than thefollowing: Pcrlite 5% above or below that given above; ltraft fiber notsubstantially more than 2% above and below; and sodium silicate not morethan 4% above and below. The asbestos fiber may vary between l5 andHowever, to obtain the advantages which should ensue with an increase,for example, in

--fiber,- the tack substance should also be increased and vice versa.For, in order to obtain the increase in strength which additional fibershould provide, there must be an increase in tack substance. On theother hand if the fiber be reduced, the tack substance can becorrespondingly'reduced without causing additional loss in strength.

Considering the various practical uses of the product and the strengthsdesired for such uses, a 10 degree B.

strength necessary for the major types of uses and a great surplus ofstrength for many uses. Such a coneentraticn. using the same ratio offiber to perliteas above, results in 23% of solid sodium silicate in theproduct. Besides providing adequate strength, if the prod ttct beexposed to fire, enough sodium silicate is in the product to form thesupp ementary reenforcing glass dc veloped on exposure to tire. Asidefrom the matter of increase in cost resulting from increasing amount ofsodium silicate, too much sodium silicate is not desirable in productsdesigned for maximum resistance to fire because too large an amount offluxed class in the product. may cause high internal stress, resultingin warping or cracking of the product on cooling.

While there are various grades of sodium silicate (varying in their sodato silica ratio) the least expensive commercial grade (having a soda tosilica ratio of l to 3.36) is satisfactory.

Except for high temperature thermal insulation (i.e. temperatures of 300degrees F. and higher) and products in which vegetable fiber isobjectionable for other reasons, vegetable fiber is preferably used bothbecause of low cost and because it facilitates manufacture by low curtmethods. For temperatures of 600 degrees F. to 1200 degrees F.encountered in industrial insulation such as pipe coverings, it may bedesirable to replace part or all of the vegetable fiber with mineralfiber such as asbestos and glass fiber. Preferably some vegetable fiberis used to git: increased wet strength. In products of this charactersodium silicate is preferable as a tack material.

Between 300 degrees F. and 600 degrees F., vegetable fiber can be usedif there be no objection to slight local or superficial charring in theregions where the higher temperatures are encountered.

While the product might be made by other methods than the abovedescribed slurry method, these are re-v garded as less economical.Substantial and unexpected advantages accrue from manufacture on aFourdrinier machine: (1) the stock or furnish may be more concentrated,as high as 8% solids, an unbelievably high concentration, the limitationon concentration being not the difiiculty of de-watering, but theflowability of the furnish, with higher solids-concentration, thefurnish might not flow with sullicicnt readiness; (2) because of thehigh solids Concentration, larger perlite particles can be included thancould be used in a less concentrated furnish because of their tendencyto float to the surface; and (3) an opportunity is afforded for removalof a sub stantial amount of water by natural drainage while the board ison the wire and before it reaches the suction boxes.

To make a 1" thick finished product, the furnish is flowed onto the wire(which is a foramincus surface) at about 2 /1" in thickness. Even beforereaching the suction boxes (a distance of about 20 feet, traveling asfast as 9 feet per minute) it has de-watered itself by natural drain ge(i.e. without suction) to a point where it is practicallyself-sustaining (i.e. dccklc boards are no longer required .0 maintainthe margins of the wet board). In passing over the suction boxes andunder the pressure and gauge rolls (but'before passing into the driers),the material comes down to about I" in thickness (e.g. about 1.04). Inthe drier it shrinks about 3 5 in thickness. Absence of substantialshrinkage is due, as stated above, to the circumstances that the productis substantially entirely perlite particles in contact and that thefibers lie in the spaces between the contacting perlite particles.

If due to the high concentration of solids, the surface texture of thestock as it lies on the Fcurdrinier wire, is rough, this roughness mayhe completely removed and a perfectly smooth top SJIfaCC produced bygentle puddling of ti surface of the stock on the wire before it rea:hestl'e suction boxes.

In mixing up the furnisl' i is advantageous to add the earpzzied perliteto a slurry conLaining the fiber (an aque- :11" of about 1.5 to 2.5%fiber concentration) with an 2;:113 anion so that the perlite particlesare fully ier d. For example, the perlite may be added to a whi lpool orvertex of the ficer stock which feeds into the bead box containing thecomentional agitator and feeder. The tack substance (e.g. emulsifiedasphalt, so-

d3::t s-l cate; etc.) may also be added to the vortex to be t3:-rc;hlydistributed throughout the furnish.

As stz'eed above, the unique chzracteristics of the expzrrded perlitemake possible the h gh concentration of solids in Le furnish, the highproportion of perlite in the prcirart, and the ready de-watering andgreat thickness :1 the board may be manufactured and the high speed offormation.

Ob-Iously the invention is not limited to the details of theillustrative embodiments thereof since these may be .-.rIo modified.Moreover it is not indispensable that all features of the invention beused co-iointly since va ious features may be used to advantage indifferent ons and sub-combinations.

described my invention I claim:

'ng essentially of about sixty percent by weight .0 of in: particle ofexpanded perlite substantially none of posited on the exterior of thefi'rers but being insufficient in amount to bond the fibers.

2. article of manufacture, an insulating material essentially ofparticles of expanded perlitc held ed form by a network of short fibersubstantially v distributed throughout the mass of perlite, the '12 of65 mesh and finer particle size with a 1 proportion as fine as 100 mesh,said perlite 3 not less than about 60% of the dry weight of theprcxiect, the fiber comprising not more than about 207: of t. -e dryweight of the product and having on its surfaces not more than about ofthe dry weight of the product of bituminous adhesive substance whichincreases the mutual friction between the fibers to give the product astrength analogous to that which would be obtainzble from long fibers.

3. A thermal insulation consisting essentially of not less than about byweight of fine particles of expanded pzrlize of 20 mesh and finerparticle size with a substantial proportion as fine as mesh, saidperlite being held in the form of a substantially thick sheet by anetwork of short fiber comprising not more than about 20% by weight ofthe dry ingredients, the volumetric ratio of p..rlite to fiber being notless than about 5:1, the fiber befsg substantially uniformly distributedin the mass of per i: but being too short themselves to provide adeq atestrength, and an amount not exceeding about 20% of the dry weight of theproduct of bitumino s adhesive substance on the exterior surfaces of thefibers to increaw the mutual friction between the fibers to prosideadequate strength.

4. The method of making a substantially thick insula- Lion board or thelike utilizing a continuously moving for-.minous surface which comprisesforming, with mixing. an aqueous slurry of pourable consistency andcontaining about sea-3% by weight solids consistingcessentially of (l)expanded perlite substantially none of which is larger than 20 mesh witha substantial proportion as fine as 100 mesh, (2) fiber, and (3) a smallamount not exceeding approximately 25% or the dry weight of the productof a non-migrating adhesive substance, the volume of perlite being atleast 5-7 times that of the fiber and the fiber being short so thatduring mixing the fiber may be unil. A th=rrnal insulation molded froman aqueous slurry -5. The method or making a thick fibrous board. or thelike. on a foraminous support which comprises making an aqueous slurryhaving a solids content consisting essen tially of approximately tl) senexpanded perlite, (2) 20% newsprint, and (3) 20'? emulsified asphalt,the concentration of solids in said slurry being not less thanapproximately 3% by weight but no: greater than approximately 8% byweight. forming on said fornminous sup-- port a relatively thick layerfroaa'such slurry of such thickness that when dry the product will notbe substantially less than one inch in thickness. dewatering said layerby removing the water through said support until the particles ofperlite are in subszanziai contact with each other, and drying saidlayer to remove residual moisture.

6. the l'l'lclhOt! of manufacturing a fiberperlite board comprising thesteps of forming a slurry consisting essentially of fibers, expandedperlite particles, water repellent organic blindcr and water, saids'urry having a solids consistency in the approximate r' go of2.872-89'6. by

weight, said expanded perlite compri ing about 60%-80% of the dry weightof the formed board, said fibers comprising about 3595-1555 of thee'ryweight of the formed board, and said binder eompr zg a substantialportion of the dry weight of the formed cs-ard, conzinuousiy forming awe: mat of said solids and draining the water therefrom, and removingthe reside-ti moisture in the mat.

7. The method of forming weight insulating material utilizing perlitecontaining a substantial portion of particles as small as 100 mesh,comprising making an aqueous slurry having a solids content consistingessentially of perlite, short fiber, and water repellent organic binder,the ratio by weight of per-51c to fiber being at least approximately 3;!and the amount or water being sufficient to form a slurry having aconcentration of solids in the range of approximately 55 .45% by weight,mixing the slurry to secure uniform distribution of the fiber throughoutthe perlite, placing the slurry upon a foraminous surfaze to permit thewater so drain from the solids deposited thereupon and the fibers to liein the interstices between the perlite particles and be held therebyagainst segregation during draining oz? of the water, and removing theresidual water by drying to render the binder efiective.

8. The method of manufacturing a fibrous pcrlitic board comprising thesteps of forming a slurry comprising fiber, water, and water repellentbinder, adding expanded perlite thereto so as o form a slurry having asoiids consistency in he range of approximately Mir-8% by weight, theapproximate ranges of percentages of the solid ingredients being BYE-15%fiber, 60%-80%' ex panded perlite, and Sk-lO'iE biaderby weight of thesolids of the ultimately formed dry board, most of said perliteparticles being capable of passing a 20 mesh screen, transferring saidsolids in the slurry to a continuously moving foraminous support to forma mat thereon, and removing the moisture contained in said mat.

9. The method of manufacturing a fibrous-perlite board comprising thesteps of forming a slurry consisting esssentially of fibers, expandedperli:e particles, asphalt and water, the solids content of said siurrybeing in the ap -roxim'ate range of 2.8924; by weight, a maior po'r-.

tion of said perlite particles being of a size to pass a 20 mesh screen,said perlite particles comprising about 60%- 8055 by weight of theresultant relatively dry board and the fiber particles comprising about3595-159? by weight of the resultant dry board, ccnzinually transferringthe slurry solids from said slurry to a conveyor in the form 14 of a wetmat while draining the water therefrom, and rerucsirz'g residualmoisture in the mat to form the fiberperlite board.

l0. II- method of forming a rapidiy dewatered in- 5 sulatien board, orthe like of substantial thickness from an aqueous slurry which comprisesmaking an aqueous slurry containing an amount not less than about 60% byweight of the soliu corstituents of the product of expander; :eriite,the partide size of which is [or th'ernost.

to part lessthan 20 mesh and s substantial proportion of which is assmall as mesh or finer, and not less than about, by weiglt of shortfiber whose fiber length is short enough to pe mit uniform dstrisutiunof the fiber throughout the man of perlite. and a small amount 15 ofadhesive material, the soiids content of said slurry' being theapproximate range of TIL-8% by weight,

agitating the slurry to eistribute said fibers uniformly thrcsghcut theslurry, transferring the slurry solids from said siurry to a conveyor nthe form of a continuous wet mat and forming the solids thereof to suchdepth as to provide a product at least an inch in thickness, the perlite pertieies holding the fibers in separated condition and againstsegregation to maintain the free filtering chamcteristies of theperlite.

It. The trethod of rmnufacturing a fibrous pcrlitic board comprising thestep; of forming a slurry of fiber, adhesive and water to a soiidsconsistency of approximately lf'e- 3% by wsight, r 'tiz'ng therewithexpanded perlite particles to font: a new slurry having a solids contentof app'oxim ttely 3'1-8'2 byweight. farming a wet mat of solids from thenew slurry on said continuously moving foraminous surface, and dryingthe mat into n board.

12. The na-thod of manufacturing a fibrous perlitie board comprising thesteps of forming a slurry consisting essenti slurry in whirlpoolagitation while adding expanded perlitic partifles thereto to preventthe perlitic part cles from floating to the surface of the siurry, thetotal solids content of the slurry being approximately 392-856 byweight, forming a mat from the sfurry solids, and dr rg the formed matto remove the residual moisture therefrom. l 3. 11:e method ofmanufacturing a fibrous perlitic board utilizing a continuously movingforaminous surface comprising the steps of forming a fibrous slurry,fonning a vortex of the slurry, adding to the slurry vortex expandedperlite particles so as to obtain proper intermixing of the ingredients,the solids content of the new slurry being in the approximate range of3%8% by weigh and forming a board from the intermixed solids on saidconzinuously moving foraminous surface.

14. The method of manufacturing a fibrous perlitic board comprising thesteps of forming a slurry consisting essentially of fiber, adhesive. andwater, adding expanded perlite particles to the slurry so as to producea-solids content in the rangeof approximately 370-856 by weight, 4

said periite relative to the fibers being in the approximate range of70-80 parts of perlite to 30-20 parts of fiber by weight, transferringthe solids in said slurry to a continu- 00 otsly moving foraminousconveyor in the form of a mat while continuously draining the watertherefrom, and drying the mat to remove most ofthe residual moisturecontained in the board.

15. The method of manufacturing a fibrous perlitie board comprising thesteps of forming a slurry consisting essentially of fiber, water, waterrepellent organic binder, and expanded perlite particles. said slurryhaving a solids content in the range of app aximately Bib-15% by weight,the perlite particles being of a nature such that most of the par iclespass a 20 mesh screen, depositing solids from the slurry upon aforaminous surface to form a wet mat thereon and drying the wet mat toremove excess residual moisture therein.

16. A method of producing an insulating board on a continuous basisutilizing a continuously moving forv of fiber, adhesive, and water,maintaining the foraminous surface, comprising the steps of V sluzryconsisting essentially of fibers, expanded perlireforming 'ing a meshscreen, the fibers comprising apprcxirn aminous surface comprising thesteps of forming a slurry consisting essentially of fibcrs. cz andedperlit: pznicies, tender and water, wherein the slurry has a sciiiscontent Wtlhin' the range of approximately 3-T' -S% by weight, forming awet mat of solids from said ssrry on said continuously moving foraminoussurface, and dewatering said wct mat.

17. A method of manufacturing an insulating lx ard on a continuous basisutilizing a continuous forzin'! a partic es, adhesive and water, thesolids COntcfii of said slurry being within the approximate range ofsea-srzby weight, said fibers compris'ng approximatcly SO'E-IO'I: byweight of the dry product. saic icrlite partie'es compzisingapproximately 402-80 '3 by weight of the dry product, amount,

and said adhesive being present in e'Z-eefive up to about by weight ofthe dry product, a wet net of solids, and dewatering said mat from saidslurry on said continuously moving foraminous surface.

l8. An insulating material consisting' essertzially of approximately4092-8096 by weight of c.\'p:tndtd erlite intertwined with a network offiber, the expanded rerlite being capable, for the mo,t part, of passinga 20 mesh screen, the fibers comprising 505-1092 by weight of theproduct and being substantially uniformly disributed throughout the massof per itc particles, and or Pic binder in effecti e amount, u; toapproximately 25% by weight of the product, assisting to hold theperlite and 'fib cr in a relatively compact mass.

consisting of asphalt, resins, and starch.

20. An insulating material consisting essentially of approximately6070-809: by weight of expanded perlite intertwined with a-network offiber, the expanded parlite comprising a substantial portion ofparticles of approximately 100 mesh or finer, the fibers compilsingapproximately %-15% by weight of the product and being substantia lyuniformly distributed through the mass of pcrlite particles, and waterrepellen: organic binder distributed in the mass and assisting to holdthe perlite and fi'cer in a' relatively compact mass. 21. A thermalinsulation consisting essentially of not ess than about 60% by weight offine particles of expanded 'pcrlite of 20 mesh and finer particle s zewith a substantial portion as fine as 100 mesh or finer, said pezlitebeing held in the form of a substantially thick sheet by a network offiber comprising not more than 505?: but

greater than 10% by weight of the dry ingred ents, the

fibers being substantially uniformly distributed in themass of perlitebut-being too short ofthemselves to provide adequate strength, and asmall but substantial amount,

not exceeding approximately 25% of the dry weight of the product oforganic adhesive substance on the exterior surfaces of the fi'ecrs andperhte and assisting to hold the mass together.

- 22. An insulating material which is essentially ex panded perliteconsisting essentially of very fine particles of expanded perlite heldby a network of relatively short fibers substantially uniformlydistributed throughout the mass of perlitc, the perlite havingsubstantially none of the particles larger than 20 mesh and having asubstantial portionas fine as mesh or finer, said perlite comprising notless than about 60% of the dry weight. of the pr duct, the fibercomprising approximately 35%-l5% of I the dry weight of the producL andsaid fibers and 'pcrlite having on their surfaces an effective amount,up to approximately 25? of organic adhesi e substance by weight,. asistng to hold theperlitc and fiber in a relatively compact mass.

23. An insulating material consisting essentially .of

comprising a substantial portion of fine grained particles ofapproximately 100 mesh and finer, the fibers comprising approximately35%-l52 by weight of the product and being substantially uniformlydistributed through the mass of perlitc particles, and organic binderdistributed through and assisting to hold the perlite and fiber in arelatively compact mass;

24. A molded light weight insulating material, consisting essentially ofparticles of expanded perlite some of which are as fine rs 100 mesh insize, the perlite particles being in substantialcontact, sail con actbeing characterizcd by point contact as distinguished from surfacecontact thereby leaving a multitude of connecting interstices betweenthe particles, and "t 'minor amount of short fiberiying n saidinterstices and constitutinga fiber network to hold said perlite in themolded shape, and an asphaltic binding constituent.

25. A molded light weight insulating material consisting essentially ofparticles of expanded perlite some of which are as fine as 100 mesh insize, the pcrlite particles being in substantial contact, said contactbeing characterizcd by point contact as distinguished from surfacecontact, thereby leaving a multitude of connecting interstices betweenthe partic es, and a minor amount of short fiber lying in saidinterstices and constituting a fiber network to hold said rerlite in themolded shape, and a binding constituent consisting essential!" oforganic material.

References Cited in the file of this patent UNITED STATES PATENTSSeybold Mar. 29, 1955 v

25. A MOLDED LIGHT WEIGHT INSULATING MATERIAL CONSISTING ESSENTIALLY OFPARTICLES OF EXPANDED PERLITE SOME OF WHICH ARE AS FINE AS 100 MESH INSIZE, THE PERLITE PARTICLES BEING IN SUBSTANTIAL CONTACT, SAID CONTACTBEING CHARACTERIZED BY POINT CONTACT AS DISTINGUISHED FROM SURFACECONTACT, THEREBY LEAVING A MULTITUDE OF CONNECTING INTERSTICES BETWEENTHE PARTICLES, AND A MINOR AMOUNT OF SHORT FIBER LYING IN SAIDINTERSTICES AND CONSTITUTING A FIBER NETWORK TO HOLD SAID PERLITE IN THEMOLDED SHAPE, AND A BINDING CONSTITUENT CONSISTING ESSENTIALLY OFORGANIC MATERIAL.